Telephone system



April 5, 1921.

w. DUNBAR TELEPHONE SYSTEM Filed Dec. 19, 1904 5 Sheets-Sheet 1ffiuc'ntorf nci Q Witnesses:

5 Sheets- Sheet 2 F. W. DUNBAR TELEPHONE SYSTEM Flled Dec 19, 1904 April5, 1927. v

.Wsses:

April 5,1927. v

- F. w. DUNBAR TELEPHONE SYSTEM Filed Dec. 19, 1904 5 sheets-sheet 5 RInventor; Francis Dun r W M M 2 v 1 927 F. w. DUNBAR TELEPHONE SYSTEMFiled Dec. 19, 1904 5 Sheets-Sheet 4 Inventor: Francis 'W Dunb r W'misses I Wit y.

F. w. DUNBAR TELEPHONE SYSTEM 7 Filed Dec. 19, 1904 s Sheets-Sheet s N 2m lltlll Witn esses:

Patented Apr. 5, 1 927.

FRANCIS w. nnnsnn, on CHICAGO, T0 KnLLose swrronnonnn &

TELEPHONE SYSTEM.

Application filed December 19, 1904. Serialblo. 237,445.

My invention relates to telephony, and has tor its ob3ect the provisionof an improved telephone exchange system wherein advantages ofautomatically and manually controlled line connectors are present anddisadvantages in these classes of apparatus are eliminated. Broadlyspeaking, I obtain these results by making these line. connectorspartially under automatic control and partially under manual control.each cord circuit that is placed under automatic control is theanswering end. Travcling switching mechanism is employed. forselectively eli'ecting connection between the answering ends of idlecord circuits and calling telephone lines The present invention (which Ishall describe in connection with metallic'telephonelines. the applica-ition of the invention to grounded lines being well understood by thoseskilled in the art) finds an embodiment in a pair of moving terminalsfor the answering end of each cord circuit and motor mechanism jointlycontrol-led by the cord connecting apparatus and a callingsubscribersapparatus. for effecting engagement between these terminals,which I shall call answering terminals, and theterminals' of a callingline. This motor mechanism has such an" association with the cordcircuits that only the idle cord circuits are automatically connectedwith calling lines. This motor mechanism is desirably not constantlyoperated, but is preferably only operated on "the initiation of a call.I preferably employ motor controlled switching apparatus governed by acalling subscriber and governing the motor mechanism that operates orcauses to travel the answering contacts or "end of an idle, preferablythe first idle cord circuit. These answering'ends of cord circuits maycomprise traveling switch arms adapted to pass over terminals of thetelephone lines and may, in one embodiment of the invention.-

be mounted on a rotating shaft operated by a motor mechanism, when setin operation by the motor controlled switching mechanism set intoactuation by a callingsubscriber. The traveling switch arms constituting the answering endsof cord circuits, hareassociated with themas many sets of line terminals there are telephone lines assigned to aparticular group of cord circuits. The motor controlled switchingmechanism, which may easily be set into The end of operation by acalling subscriber, is so interrelatecbwith the cord circuits andelectromagnetic mechanism governing the operation of the motor mechanismactuating the answering terminals of the. cord circuits, that only suchcord answering terminals that are associatedwvith, idle cord circuitsare operated by the motor mechanism inmechanical relation therewith. Inwords, inthe embodimentof the invention herein specifically set forth,the calling subother fill scribe]? causes the motorinmechanical'a'ssociation Wltll the answering end ofi-an, idle cordcircuit to bring said terminals intoconnection with-the terminals of acalling line. Upon such connection of the answe'r ing ends of an idlecord circuit witlra call-- ingzline, the motor belonging tothe cordcircuit is caused to stop, preferably by means of electromagneticmechanism whose {circuit conditions arechanged upon this estabcircuitand a calling line, such electro-mag netic mechanism thereupon effectingthe stoppage of the, motor, wh ch result isaclishment of connectionbetween anidle cordcomplished where the motorisv anelectric motor,preferably by altering the circuit of said motor. 'Where an exchange hasalarge number of lines, the lines are preferably .dividedinto groups, aparticular number of cord circuits being assigned to eachgroup. Inorderto'prevent undue cost: of the er;-

change equipments, the motor controlled switching mechanismgoverned by acallin subscriber is preferably common to all lines at v ot' the group.there being as-Jnanysuch switching mechanisms as thereare groups. I donot wish, however, to' be limited to common to a' group oflines,conductors from such an arrangement. Where such motorv controlledswitching mechanism is made all the cord circuits belonging toaparticu-,

lar group are placed in. electrical association therewith and saidswitching mechan ism 1 caused to. travel over terminals of theseconcluctors. The electrical'condition of these terminalsfdepends uponthe condition of use of the cord circuits. are idle. the electricalcharactergot the ter-' minalsfi's such that when the motor" .1co'natrolled switching device comes into contact I with the firstof suchterminals associated 1 with an idle cordcircuit, the electro-mag-(nu-.10 mechanism is operated to permit" the actuation of the. cordcircuit motor corresponding tothe saidterminals whereby the answeringterminals of the cord circuitcor responding to the cord circuit motorare caused. to engage theterminals of a calling line, whereupon'saiclVcord circuit motor is ith'rown out of action. When the terminalsengaged by the motor controlled switching device have their associatedcord circuits busy, the electro-magnetlc mechanism 1mmediately governingthe operation of the cord circuit motor-Elias no operative eifect uponsaid cord circuit motor, which thereby remains quiescent.

I shalliterm the motor controlled switching device governed by callingsubscribers, the 'subscribers governor motor, and the motor whichdirectly oper-,

'ates the answeringiterminals of a cord circuit, the cord circuitanotor,as such terms have been previously used. g

" means of my invention resides in the adapt-r A-very importantadvantage gained by ability' of mynovel apparatus to telephonelines'already equipped in which-relays were originally installed for thepurpose of operatingfline signals. In order that special l ne signalsmaybe dispensed with, a signaling device, preferably a signaling lamp,isassociated with each cord circuit and suitable governingapparatuswhereby it may manie feet a signaltothe operator when a calllngsubscriber initiates a call. 'Ihave, thus, gen- "erallydescribedthemechanism by which the answering ends of idle cord circuits areautomatically connected with calling telephone lines.

In order that a connection between ajcallingand a called subscriber thusinitia'ted may be completed, the connecting ends of the'cord circuitsareprovidedwith 3connectingplugs and the telephone lines are g )rovi'ded with line jacks adapted to rece ve This provision ofa line jack toeach line,-in addition to the multiplcd terminals of each line that areassociated with the traveling answering terminals of thecord circuits isan important feature of connecting plugs.

my invention, inasmuch as by its provision theconnecting end of eachcord circuit'may,

"in conjunction with its connecting plug, be under the manual controlofthe operator. VVhile'fmy invention has found particular utilityin'connectio-n with and is well adapted for application to multipleswitch-board systems, it, has other applications, whichwill be readilyunderstood by those skilled in theart, 'VVhere. the invention isemployed in connection with multiple switch-board systems the telephonelines may be connected {with the different sections of the switch-.board in accordance with any: suitable .prac- :tice, as" the apparatusof my. invention does not interfere 111 any way with the usual operation and arrangement of the operators liss tening keys, ringing keys,testing I facilities,

and'thersupervision ofthe called Subscribefis nne. inasmuch asthew-answering end of of the different operators. skilled operator canproperly attend to 270 calls in an hour if the calls be uniformlydiseach cord circuit is changed in the manner specified, I have providedsupervisory sig-. ,nals for the calllng line whlch are brought In thepreferred embodiment of my invention, the answering terminals of cordcircuits are always restored to an, initial position, which result isdesirably accomplished through the agency of electroI-magnetic apparatusgoverned by the cord circuit and having its operation dependent upon thewithdrawal of the connecting plug.

Another feature of my invention relates tothe distribution of work amongthe operators, and by this feature of my invention a wide range offlexibility in such. distribution is effected, particularly in the caseof multiple switch-boards In multiple switchboard practice it is wellunderstood by those skilled in the art that each line has, in additionto the multiple jacks distributed throughout the boards of the system,an answering jack and'a line indicator, the answering jack and indicatorof each line being collocated. These indicators and jacks aredistributed in groups of uniforni.quantity among the diiferent sectionsof the switch-board,- so that there is disposed at all operatorspositions the same number of answering jacks and the samenumber ofrlinesignals. It is, of course, apparent thattelephone operators possessvarying degreesof skill and speed in handling calls. I The uniformdistribution of answering jacks and line indicators renders it difficultand impracticable in accordance with present practice to apportion workto suit the capacity The ordinary tributed throughout the sixty minutes.The average time or length of each call is, approximately,'one minuteand twenty seconds, thus, allowing each cord circuit vto complete ascalls per hour if kept busy throughout the sixty minutes. Sixcordcircuits keptuniformly busy throughout the hour can, therefore, handle270 calls during the hour-the work of the ordinary operator. Certainoperators can, however, handle in a proper manner more than 270 callsper hour, while others, less skille a e unab e to handl properly as manyas 270.- I preferably provide means whereby one or more cord c1rcuits.at each operators position may be thrown out of operation or out ofoperative relation with respect to the line circuits, wherebyeachoperator may be given as many cord circuits in operative relation tothe line circuits as can be properly handled by her. Thus, certainoperators may have but three or four cord circuits in operativecondition, while others, highly skilled, may have eight, nine, or eventen cord circuits placed in operative relation to the calling lines. Bythis means each operator may be kept as busy as her degree of skill-willpermitand paid according to her ability or skill, the number of 'cordcircuits which she can efliciently handle being a correct gauge ormeasure of the number of calls which she can efficiently handle perhour.

It may be properly assumed that oneeighth of the total number of callsmade during the entire twenty=four hours of the day will occur duringthe busiest hour. The switch-board must be designed to handle thebusiness at all hours of the day. Consequently the number of sections ofswitchboard is determined by the number of operators required to handlethe business during this busiest hour. If, during this busiest hour-or'moment,each operator be 'employed' at her maximum elficiency, thenecessary switch-board equipment will be minimum. In the present systemsof manual telephony it is customary to provide an intermediatedistributing board whose function is'to present facilities fordistributing the answering spring-jacks and calling signals throughoutthe various sections of switch-board, so as to cause as uniform adistribution as possible of'the calls during this busiest-houror moment.At best, however, owing to the daily fluctuations'in the amount-ofbusiness from certain groups and from all classes of lines, it isimpossible to distribute the said jacks and calling signals so as tosecure more than a rough approximation to a uniform distribution ofcalls. By means of my invention, however, a distribution of calls may beautomatically secured, such that when the number of cord circuits inoperative relation with the calling lines is properly proportionedaccording to the skill of the individual operators, each operator willbe working at her maximum efficiencv not only during the busy hour, butat all hours. Consequently the necessary number of sections ofswitchboard will be decreased and fewer operators at all hours of theday will be required.

In all present manual systems of telephony the calls at all hours of theday are distributed throughout the entire switchboard, this requiringthe presence of one or more operators at each section of theboard atalltime's save. certain of the nightliours when the business so slack thatfrom one to ten operatorsdepending upon the size of the exchange-canhandle the entire number ofacalls by walking from section to section andpicking up the various calls as they may come in. At all such times theefficiency of the o1")'eratorsreckoned on a.

ing upon the size of the exchange and the volume of night business, sothat as the business increases operator after operator may be addedasrequiredthe' first or lower numbered sect-ions being always busy andthe higher numbered sections coming gradually into operation as thebusier hours approach. I am, thus, enabled to secure the same averagenumber of calls answer-ed per operator per hour throughout thetwenty-four as is secured during the busiest hour of the dayresulting ina decrease in operating expenses of 50% or more. I do not contemplate,however, in large exchanges providing the necessary switchingfacilities, so that each line may be connected, with any one of all thecord circuits, although in'smaller switchboards it would be preferableto do so. In large exchanges I prefer to dividethe lines into groups ofseveral hundred each and divide the cord circuits intoa correspondingnumber of groups, so that any line in .a certain group may be connectedwith any cord circuit assigned to that group if the lower numbered cordcircuits of that group already be busy, and if that particular one benot busy. The first idle cord circuit ofthat group being thus selectedwill automatically make ctmnection with a calling subscriber. Forexample, I will assume an exchange of 4,500 lines and provide a group ofthirty cord circuits for each 500 lines, thus, making two hundredseventy cord circuits in all. divided equally between nine sections. ofswitch-board, or thirty to thesection and ten to the operator. Duringthe night hours, therefore, all callswould appear at the first sectionof switchboard, unless in some particular group of 500. lines there weremore than three calling lines simultaneously c011- n-ected forconversation-in which case the fourth lineiof that group making a call,'

While the three other calling parties of. the same group werestillconnected, would indicate atthe first position of the second.section. -A-fifth call fromv the same group 00- would require, assumingone operator only was required for the business at this time. thatfive-sixths of the total business which this single operator couldefiicieiitly handle was originating inaa group containing only onerninthof the total number of lines.

:In the example chosen .as an illustration.

I would employ thirty selector switches for each group of 500 lines,-each selector switch including 500 sets of telephone line terminalcontacts. The travelinganswering terminals oftlie cord circuitsniove'over'their companion sets of line terminal contacts when theircorresponding inotorsiare set into operation. Thus,'ea'ch line hasthirty sets or line terminal contactsin cooperative relation with thetraveling ends or terminals of thirty cord circuits and each cordcircuithas its traveling answering terminals in cooperative=relation with 500sets of telephone line terminal contacts. I

In the preferred embodiment of my invention, the first cord circuit hasits answering end connectedv with the connecting plug appearing at thefirst operatorsposition'ot the first board, the second cord circuithaving its answering'end connected with the connecting plug at thesecondoperatorswposition,

[the third cord-circuit having its answering end connected with theconnecting plug at :the third o-perators position, the fourth cordcircuit having its answering end connected with theconnecting zplug atthe first operators positionatthe second section of the switch-board,the-fifth .cord circuit having @its answeringend connected with theconso on.

necting plu'g'at thesecond operators position of ithes'econd section,the sixth cord circuit having its answering end connected with theconnecting-plug at the third operators position of the second section,and I'have indicated ten plugs at each operators position and, in orderthat no ''operator may receive calls to such an extent that she cannotattend to them, provision is made whereby cord circuits may be na-de tocorrespond with busycord circuits, in order that when a less efficientoperator has reached her capacity, the cord circuits which have beenincapacitated, will not be connected with a calling line, but, on theother position.

hand, such calling line will be connected with the cord circuit atanother o-perators thirty cord circuits is worked to its maxi mumefliciency, the cord circuits will be cap'able or handling forty-fivecalls per hour,

or'a' total of-one thousand three hundred fifty calls during. the busyhour, represent- Such a condi- It will be seen that if each of the iiigan average of 2.7 calls per subscriber during the busy hour, or 21.6-per subscriber per day. ,A'mple margin is, thus, present furnishediorhandling a greateriiumber of calls per day: than will originate in anaverage exchange of the size chosen as an ex ample. I

As stated, my invention contemplates neans associated with selectedswitches for rendering impotent those cord circuits each or anyoperators position which it may be desired to cut out of service, sothat the selective switches will pass by those cord circuits thusrendered impotent as though they were already in use. I

I will explain my invention more fully by reference to the accompanyingdrawings, in which- Figs- 1, 2, 3 and iillustrate preferredenibodiinents of the invention.

'Fig. 5 is a general diagrammatic view illustrating one distributionofythe cord circuits, which may be varied to suit different exchanges.

Like parts are indicated by similar characters of reference throughoutthe different figures. I

Each subscribers station AB is provided with customary common batterysubscribers apparatus, the switch hook at each station servingoperatively metallically to unite the sidesol the line when the receiveris removed. I. do not deem a detailed descriptionof the subscribersstation apparatus to be essential, as the illustration is sutlicient-tomake the same understood by those skilled in the art. Although I haveillustrated one arrangement of subscribers station apparatus, it will beobvious to those skilled in the art that other arrangements may beemployed at the sub-stations, and I do not wish to be limited toflthearrangement and apparatus shown, nor do I wish to be limited in allembodiments of the invention to its application to a common batterysystem. -The subscribers lines indicated are metallic lines and eachextends in two branches to the exchange, where they terminate inarmatures' 11 of a cut-off relay 2. The alternate contacts of thearmatures, those contacts that are engaged by the arinat'ures when thecut-off relay is energized, constitute terminals of the office end ofthe line which is supplied with the line jack 8 that I have spoken of.The system illustrated being a multiple switch-board sys: tem, there arealso provided upon other sections oi. the board than where jack '3 islocated, other acks 4 in connection with the said alternate contacts andthe oflice endot the line similar to the connection of jack 3. Thatwhich in a multiple switch-board in circular rows over which sweep theanswering terminals 7'8 and 78, which answering terminals are desirablynot normally connected with the balance of the cord circuit, but which,as indicated in connection with the terminals 7-8, are caused to formcontinuations of the cord circuit upon the operation of an armatureswitch including a tip switch contact 9 and a sleeve switch contact 10governed in their movement by a relay llnndei' circumstances to beherein after set. forth. There is'also an additional circular row ofcontact buttons 1212 over which sweep contact arms 1313 that take partin controlling the motion of the terminals 7-8 and 7-8. The number ofcontact buttons or terminals 5 and also 5, the number of contact buttonsor terminals 6 and alsoG" and the number ofcontact buttons or terminals12 and also 12, each equals tens 6 equals 500, one connected with eachline,'and the number of contact buttons 12 equals 500, one for eachline. The contact arms or brushes 7, 8 and 13 constitute a set and thereare as many sets of such contact ln'ushes as there are cord circuitsassigned to a group of telephone lines. Said contact arms of each setare desirably operated by 'a common prime mover, there being a shaft 1%forming a part of the common prime mover upon which it may be understoodthe arms 7, 8 and 13 are mounted. There are, thus as many prnne moversas there are cord circuits. The prime mover 15 illustrated upon thel-eftof each of thedrawings is composed of a spring motor 16 in crivingengagement with the shaft 1e and awheel 17 upon said shaft, which wheelis "provided with a plurality' of off-set teeth 18-19 arranged 1nperipheral rows, across which teeth the polarized armature 20 of themotor is adapted to oscillate by the agency of the field windings 21 andthe source of alternating current 22 when said source of current isincluded in a closed circuit with said windings. The said armature moperating, is removed from engagement with one tooth 18 mto the path ofan oif-set tooth 19, whereupon the spring motor may .move the wheel astep, whereafter the armature is oscillatedto its initial position intothe path of a new tooth 18. that is offset with respect to thepreviously engaged tooth 19, whereupon the spring motor may move thewheel 17 another step, and so on, until the source of current 22 has thecircuit including the same opened.

In the motive device shown upon the right of Figs. 1 and 2, a source ofdirect current, as the common battery 23, may be employed to operate thefield winding 2a, which is alternately energized. and de-energized, so

that the armature 25 may be attracted from engagement with the teeth inthe row 26 and brought into the path of the teeth in the row 27 off-setwith respect to the teeth 26. Upon this attraction of the armature, thecircuit through the magnet 24 is opened, whereupon the spring 28restores the armature to its initial position. a ln'this way a springmotor, which is assumed to be in driving engagement with the wheelbearing the teeth 26'27, may cause the answering terminals of the cordcircuit to move from one line contact to the next, upon thede-energization of the magnet 24, and as the result of the retraction ofthe spring 28.

I will explain the circuit arrangements of the magnets 21-24 and theapparatus by which such arrangements are controlled more fullyhereinafter.

When a subscriber initiates a call, the

answering end ofan idle cord circuit in this case the first, isautomatically connected with a set of terminal contacts, asthe contacts5 6, for example, this automatic connection being occasioned by theoperation of the said cord circuits motor. Only one cord circuit .motor,that corresponding to an idle cord circuit, is preferably operated inautomatically effecting the movement of the answering terminals of saidcord circuit.

1 lo into contact witlrthe terminals of a calling 11116; To thls end, Ipreferably employ select ve mechanism, constituting an electric motor.that serves to select the cord circuit motor that is to be operated,which selecting motor may be termed the calling subscribers governormotor and there is preferably only one such motor common to a group oftelephone lines. Referringa'gain more particularly to the systemillustrated in Fig.1, this governor motor includes in one embodimentofthe invention a traveling switch 29 operated by the armature of. anelectrosmagnet 30, as will hereinafter be particularly set forth, whichswitch. 29 rides over a series of contact buttons 31, constitutingterminals of conductors extending to 'the'variouscord circuits of agroup, there being as many contacts 31 as there 'arecords ot apartlcular'lot assignedto a group of lines; there are the example chosenthirty such contact buttons 31; A complete conductor 32 is shownextending from one of the" contact buttons 31 to the cordcircuititliatis shown uniting the subscribers sta' tions A and B;

Normally, that is, whenits cord circuit is idle, this conductor 32 isconnected with the grounded battery 23 by way the armature switchconstituting a terr so.

, into operation.

oft-he switch 33 governed by the relay 11.

Tlife switch 29 is normally disconnected, from gro ui'ichbut, as willhereinafter be more fully setforth, has ground connectedtherewith by asubscriber in initiating a call, whereby the circuit includingtheconductorv32 is co npleted. The winding of a magnet is included inthe conductor 32, sothat, when this conductor is included in a closedcircuit,

minal of the generator 22, is attracted to complete the circuit throughthemagnet 21 andsaid' generator, theswitch 36 controlled by magnet- 11,then being upon its grounded contactf l/Vhen therefore, the switch 29 isi moved. by a, calling subscriber into connec- ;tion witha conductorthat s completed matically connected with a calling line,- said switchiscaused to pass said opened con-- ,ductor and to continue its operationuntil it enccun'tersa conductor that is closed. at

33', that is, a place similar to When the switch 29 encounters theterminal of, a conductor that is closed at and the corresponding cordcircuit motor has iiiovedthe switches 7-48: into connection with thetelephone' 'line terminals and the switch 13 into connection with the"conduct-or associated with the calling telephone line the magnet llbecomes energized in a manner more fully hereinafter to be set forth,-to operate the armature switches 9'1( );to, complete the connection oi?the cord strands witlithe said line'terininals,'to open the conductor at33, to open the c rcuit of the cord circuit "pr me mover at 36, and toclose a subsidiary o path through the winding of magnet 11, to nainta nit energized irrespective v of subsequent changes occurring. in theapparatus associated with the calling line, the. arma-' ture switch, 87engaging its contact, which is =a pivotedonebetore said contact breaksconnection with the contact it in turn normally engages. As one of thevresults. of

I the posit-ion. to. which by its operating motor.

' -these'circuit changes, the cord 'circuitmotor ---ceases itsopeiatiomsonthat the answering end oi, the, selected cord oircuitmayremainit, has. been placed f' llavi ig thus a general way outlined someof the operations taking place in autorelay 45.

matically effecting connection between a calling subscriber and an idlecord circuit, I

1 will now more particularly describe the invention. I

The subscriber, as A, having initiated a call, includes the winding of amagnet 35 nected with acondu'ctor 41'that is common to all of the linesand which extends to the switch 29 and which isthe conductor thatoperation of the apparatus entering into my grounded before. 40; Theswitch 39 is conis grounded in order to complete the circuitcontainingthe conductor32, when said latter conductor is closed at 33 asheretofore set forth, whereby results that have hither-' to beenspecified are accomplished. This same conductor 41 has a branch 42 thatis connected with the grounded battery 23,

which conductor 42 includes the'winding of the motor 30, the switch'arm43 governed in its operation by the armature of said motor 30 and thearmature 44 with its contact, said latter armature belonging to thegrounded at 39, but the magnet 30 is included in a grounded circuit,which circuit is intermittently opened by the separation of the lazy arm43 from its contact due to the operation of the armature of the magnet30 andthe cooperation of an extension of said armature between thebifurcated ends of said arm. The arm 43 is forced away from its contactupon the attraction of the armature by the magnet 30 and is restored toengagement with its contact by the spring in connectionwith saidarmature, the said armature being thus intermittently attracted as longas the circuit containing the magnet 30 is otherwise closed. Saidarmature cooperates with the teeth of an extension of switch 29',whereby the said switch is caused to travel as thearinature isintermittently attracted. The dog 46 engages the said teeth to preventthe restoring spring 47 from operating until required, so that theswitch 29 is maintained in any position, for the time being, in which ithas been placed by the magnet 30. WVhen the switch 29' encounters aconductor 32 that is closedv at 33,'circuit through the magnet 45 isobviously closed, the winding of this magnet being included in theconductor 41, whereupon the armature 44 is vattracted to bring the catch48 into connection with the catch upon the dog or detent 46. preparatoryto releasing the said detent from mechanical locking engagement with theswitch 29 to permit the spring 47 to restore the said switch to itsnormal or initial position. The magnet 45 remains energized until thecircuit containingthe conductor 32 is open at 33, which only is Thus,the switch 29 is not onlyaccomplished when the cord circuit motorselected by the subscribers governor motor has broughtv the answeringcontacts of' its associated cord circuit into connection with callingline terminal contacts The connectionof the cord circuit with thecalling telephone line having thus been effected, circuit through themagnet is opened at 33, whereupon the spring 49 lifts the dog or detent46, permitting the spring 47 to with: draw or restore the switch 29 toits initial position. In order that the .switch 29 may not through somefault in the operation of the apparatus, or in case all cords are busypass all of the contacts 31 without causing the selection of a cordcircuit and thereafter be not restored, I provide a supplemental contactbutton 50 which is engaged by the brush29 on reaching the limit ofits-excursion, whereupon circuit is completed that may be traced fromthe ground at 39 occasioned by the calling subscriber, the magnet 45,the switch 29, the contact button 50and the grounded battery. 23,whereupon the armature 44 is attracted, with the results hithertospecified, the circuit throughthe magnet 45 is opened at 51 and thespring 49 is permitted to witlrdraw the detent 46, whereupon the spring47 restores the switch 29. In order that some of the cord circuitsmayberendered inoperative, so that work assigned toless eflicientoperators may be reduced, he conductors 32may each include a switch 52that. may produce a break in said conductor similar to, that produced.at. 33 when the magnet 11 is energized, sothat the switch 29 will notpauseiat a contact terminal of said conductor, but will pass the same ias if the cord circuit associated therewith werebusy. In order that myinveniton may be effectively practiced, the magnet 11 which is, the onethat determines the connection of the selected cord circuit with thecalling telephone line, determines the continuity of. the circuitincluding the governor motor, and controls the electrical character ofthe buttons 31 by controlling the conductors 32 at 33) is preferablyincluded in a circuitthat is distinct from the talking circuit, whichcircuit includes a conductor 53 that terminates in the armature switch40, there being one such armature switch 40 and v one such conductor5,3. for each telephone line. This conductor 53 is connected with thecontact buttons 12'.12, etc. associated with the cord circuits, therebeing, as hitherto stated, as many such contacts 12 and as many suchcontacts 12 as there are telephone lines in a particular group. Theswitch arm 13, for example, cooperates with the contact buttons 12, thesaid switch arm moving with the switch arms 7-8 until it encounters theconductor 53 that is grounded at 40 by the calling subscriber, whereupon circuit is closed from .saidground at '54 engaging its normalcontact 55.

40 through the grounded battery 23 by way of the switch arm 13, thebutton 12 engagi mg the same and the pivoted switch contact magnet 'llisthus energized to bring the switch arms 91O into connection with thecontacts of the calling subscribers line, while the armature switches33, 36 and 37 are moved by sald magnet when-thus energized, whereby thesaid magnet is included connected with the tip strand of the cordcirc'uitand which ground is reached over the subscribeids line by way,of the answering terminal 17 and the armature switch 9. The magnet '11will thusbe unresponsive to any change in the position of the switch-4Oand the cut-off relay ]2 will be energized, whereupon the armatures1-1will be attracted and the switches 3940 restored to their normalpositions, the. said armatures 141 being thus connectedwith theiralternate contacts, whereby the connection between an idle cord circuitand a calling line is completely established, Upon such "a completion ofthe connection of a selected cord circuit and a calling-line, thecalling indicators 59'60 are' operated in a manner to be specified,whereupon the operator includes her telephone outfit in a manner wellknown, in circuit with the. calling subscriber and, after hav ngascertained the The 105. connection he desires, inserts the connecting vplug 61. of the cord circuit corresponding to the signals 59-60 into theline'jackof the subscriber desired by subscriber A. and

thereafter signals the called subscriber .in

l l O the usual way. Before the connecting plug 61 hasibeen inserted,the magnet 62 is in i open circuit, its armature falling away therefrom,whereby the pivoted contact 63 may rest against its-normal contact, sothat,

when the magnet 58 is energized through the agency of the callingsubscribers apparatus, as has been specified, circuit through thecalling lamp 59 may be traced as follows:

from the grounded relay 64 through'said lamp 59, the attracted armatureof magnet.

58, the normally placed pivoted contact 63,

the contacts 56 56 the conductor 56,. to:

.terv 23. When the operator inserts the plug 61 into'the jack of acalledv subscriber,- the .the grounded battery 23,. causing the.'callmagnet 62 is energized-by being includedin a circuit that containsthe grounded battery 23, the {winding' ofsaid magnet 62, the

sleeve strand of the cord circuit, the sleeve of the inserted plug andthe winding of the I groundedcut-o-tf relay 2. The armature of themagnetfor relay 62 is thereby attracted to movethe pivoted contact 68from its normal contact, thereby opening the circuit including thecalling lamp 59 and the relay .64, whereby signals occasioned by thelamps 9 60 are effaced- The supervision over i 'the'called subscriber ishad by thelamp 65 circuit illustrated. I do'not, therefore, deem vaiparticular description of the apparatusby .which the lamp' 65 iscontrolled to be essen controlled by the well known cord circuitapparatus at the connecting end of the cord tial; The supervision ofthecalling subscribers telephone-line is had by the lamps j 67-68,whichsupervision may begenerally 'des'cribed'as follows: When the; cordcircuit has been automatically connected'with a call 4 ingl'ine, circuitthrough the magnet 57 is completed,the calling subscribers telephonebeing off" its hook, as has heretofore been specified, which circuit maybe traced from thegrounded battery'23 through the wind-- v inggof'themagnet 57, the sleeve strand of the cord circuit, both limbs of thetelephone line, back to the tlp strand of the cord circuit and thegrounded magnet 58.

The armature switch 69 operated by the, magnet 58 is, therefore,attracted, so that the circuit including the lamp 6? is opened.

IWhen-thecalling subscriber is through and has restored his telephone,the connection of themagnet 58-wi-th the battery 23- is interrupted atthe calling subscriberls switchhook, but themagnet '57 still remains incircu-itwith said battery, as it is lnclud'e'd be tween the-ground ofthe cut-oif relay and I the said battery. Release of the armature I 69,therefore, completes circuit through the lamp 67, whichumay be tracedfrom'the grounded battery 23'through said lamp, the

armaturefswitch of the relay 57"- connected ,with the-lamp,' the"armature swlt'ch 69, to

'j 68 isla supplemental signal that is prefer- "any employed, for whichpurpose a relay or v mag-net TOis -includedi in" circuit with the a '55'laniptl, so that circuit through the lamp thegrounded contact engagedby said armature, switch when thus released" The signal'68isestab'lished by the armature of magnet -70 when attracted, whichcircuit may be traced f'rointhe grounded contact engagedbysaiduarmat'ure or armature switch, the 6. lamp-"68, to thegrounded-battery. The elemerits. 70, 68, 64 and are preferably common-toa number of cords.

' I When the subscribers have finished conversation-and have resto'redthfeir receivers, the supervisory indicators 65, 67 and '68 1ntime thefact, whereupon the operator withdraws the plug 61.- This withdrawal ofthe plug causes an, opening of the circuit including the magnet 62 atthe jack that 7 contained the plug, whereupn the pivoted.

is disconnected from its circuit The 1 magnet or relay 11 becomingthereupon de energized, releases the armature switches 9, 10, 33, 36 and37, whereupon the calling line isautomatically disconnected-and the cordcircuitis restored to its idle condition of The selecting mechanismillustrated upon the right of Fig. 1 is generally similar tothatillustrated upon thelcft. The cord circuit motor operating theanswering end of the cord circuit shown in association therewith is ofthe same general character as that illustrated upon the left of thedrawing, but the escapement 25 is operated through other agency than isthelescape- Y ment 20, the eseapement 20 being moved alternatelyaltogether by magnetic attraction, while the escapeinent 25 is moved'inone d'ir-e'ctionby the magnet '24 and inithe' other direction 'by thespring, 28. Teethfi26-27 are-also preferably spaced with respect to eachother somewhat-dififierently' from the teeth1 819,-so that, when thedetent 25 is disengaged from a tooth 26, the wheel carrying the teeth ismoved a lesser distance than when said escapement 1s disengaged from atooth 27, to be brought into connection with a tooth 26'. This permitsthe answering end of the cord circuit to be very quickly operatedwithout danger of moving the same beyond the line terminal contacts of acalling subscriber. The apparatus upon the right includes similararmature switches 9v 10 associated with the'answering terminal coni justas in the left of the drawing. The magnet 71 operates the switches -9 l0for the same purpose that r the magnet 11 operates: its armatureswitches 910; The magnet24 is included in a circuit that contains "thebattery 28 and the bifurcated lazy arm 72 when engagedwith Thesubscribers governor motor upon the right of the drawing is similarinconstruction, operation and arrangement to that shown upon the left ofthe drawing, like parts and connections of both governor motors beinggiven similar characters of reference. Other part's'ofapparatus an'dcircuits illustrated upon the right of Figfl armature its groundedcontact through the agency of the spring 28;

that have functions and arrangements corresponding to similar parts uponthe left of the figure, are also. given similar characters of reference,though in some cases the mechanical association may not be absolutelyidentical. ductor 32 has been closed upon the select-ion of an idle cordcircuit switch by the calling subscriber (now speaking of the apparatusupon the right), the magnet 3a is operated to attract its armature andcomplete circuit 1' irough the magnet 24:, which may be traced from thegrounded battery 23 through the magnet 24, the armatureof magnet 3a, tothe bifurcated lazy arm 72, when engaging its grounded contact. A tereach attraction of the armature 25', circuitthrough the magnet 24 isopened by the separation of the lazy arm 72 from its groundedcontact,wvh ereby the armature 25 is released and is thereupon removedto a reverse position by the spring 28, which spring at the same timecauses the restoration of the lazy arm toqits initial position,whereupon circuit through the magnet is again closed which operation, iscontinued until the cord circuit motor has oper- V atcd the answeringends of the idlecord circuit, to bring the same into connection witha-calling subscribers hnetermmal contacts. hen this result is ach eved,the arm 13 is grounded by way of the armature switch ll) of the callingsubscriber, whereby the magnet 71 is included in a circuit that may betraced from the grounded battery 23 through the magnet 24, the armature35, its contact,

the magnet 71; the switch arm 13, to the grounded armature switch d0,whereby the armature 25 remains attracted by the magnet 24 and wherebythe magnet 71 is energized. The energization of the magnet 71establishes a supplemental circuit for the magnetQ l which may be tracedfrom the 71 and grounded battery 23 through said magnet 21 the contact73, the armature 74 of magnet 71, the winding of magnet 71, the armature7 5, to the conductor 56 that has a ground established thereupon, theground being indicated in dotted lines. After a calling line hasselected an idle cord circuit,

the magnets 24: and 71 are maintained ener gized until the cordagainbecomes idle. Another result of the energization of the magnet 1 isapparent in the de-energization. of the magnet 3 1, whereby the governormotor may be restoredwithout the danger of being re-steppedatthe end ofa connection. The provision of the circuit afforded by the armature 75and the ground upon conductor 56 is for the purpose of maintainingcircuit through the winding of'magnets 24:; which otherwise would bebroken upon the disconnection of ground from the armatureswitch 40 uponthe operation of. the armature switches 91-10 which cause in the mannerheretofore set forth, the opera After circuit through the con "tion ofthe cutoff relay 2 and the consequent that the switch 29, being thenreleased, would immediately select the next idle cord circuit, owing tothe ground still present on conductor 41, this operation continuinguntil all l1 I l h 01 is call ng ,su sciioeis in a gioup ave beenanswered.

A feature of my invention resides in the provisionofthe supplementalsets of contacts 1212 in addition to thetalking terminals of eachtelephone line inconjunction with the switch arms 13-13 cooperating withsaid contacts. a

A very usefulfeature of my invention is theprovision-of local circuitsincluding subscriber operated switches, ls l0, desirably located :atthe-exchange and adapted to include a switch arm as 13 in circuit whenplaced in engagement with one of the said supplemental line contacts as12 and'apparatus included by said arms in any local circuit thusestablished, which apparatus will serve to eifectthe restoration of thecord selecting mechanisnnso that said mechanism may be used inperfecting otherconnections. I

in the precise embodiment of the inven tion illustrated there are, ashas beenstated, as many supplemental line contacts12 and as manysupplemental line contacts 12" asthere are telephone lines in aparticular group. ,There are as many sets. of these contacts 12 12" andarms 13%13 as there are, cords assigned to suchgroup. In the embodimentof the invention illustrated.

there'are thus many moreisubscriber operated switches 4IO provided forthe local circuits V llO than there'are sets of contactbuttons 12- 12and arms13,13,-but the said arms and contact, buttons are adapted to beincluded in local circuit with switches 40,015 calling lines; I donot'wish to be limited, however, to the precise arranged illustrated.

The system illustrated in Fig. 2 is similar in general respects to thatindicated iIrFig. 1 The system illustrated inFig'ZhaS as a modificationof the system shown in Fig, 1

additional sets of subscribers contacts 76'76 equalling 5-5, 6+6, etc,arms 77 for 767,6 and circuit conductors 7879, in

the; provision of switch which conductor 78 there is included an";

auxiliary armature switch 80 and relay 81 in number the, contacts sets.of added contacts and in which conductor- 7 9 there is included thecut-off relay 2,-the conductor'79 being 7 extended to the multipledspring jacks, the

oarticular s stem shown bein a multi le switchboardsystem,wherebythecut-ofi relay may be Operated from'any section of theboard as well asupon theconnection "of the answering end of a cordcircuit with a calling line. In the system shownin a side o of "thetalking circuit is employed in the operation of the relay 2, whereas inthe syspurpose o-f 'this control of the-cut-ofi' relay and the controlof the supervisory apparatus associated with the cord circuit.- Theparts of the system illustrated in Fig. 2 haying the same generalpurpose and arrangement as those illustrated in Fig, 1, are given simi-'lar reference characters; I-n general, the

' functions performed by the added conductor are similarto the functionsperformed by i one of the talkingconductors shown in the a system of 1.The supervisory relay 81 corresponds in function to the supervisory"relay '57, the supervisory relay 82 cor-. responds in function to thesupervisory relay [58, the supplemental supervisory relay 83 Vcorresponds in function tothesupple-mental if "p'loyed throughout theUnited States in large -exchanges, the two being illustrated in orderthat the wide applicability of my ini It'will have function oftheiswitch 29 and the elements supervisory relay 70, and thesupplemental 1 relay {84; corresponds 1-11 function to the sup- '3plemental relay 64:. The la 111ps8.5,86,'87 and 88 correspond'infunction to 'the lamps 59, .60, .67 and 68. Theap-paratus associatedwith the connecting endof the cord circuit is well understood by thoseskilled in the art and need not further be described, except to*statethat a relay 89 correspondsin function 'f to the relay 62 of Fig.-1=is added. The cord circuims in accordance with well known practice. l"have indicated in F gsLl and 2 those systems that are most vcommonlyemvention' maybe readilyunderstood. I do not deem it essential toillustratefurther systems and the; application of my inyention thereto.

In "the-system illustrated in Figs. 8 and I r .4 the'same generalsystemshave been illustrated that are shown 1n Figsl and '2 re spectively;

been observed that the main in cooperative relation therewith has beenperformed as soon. as a cord circuit motor corresponding to an idle cordcircuit has,

been set into operation, the saidvswitch 29 being restored to'itsinitial condition as soon,

as the. selected cord circuit motor has brought the answering end of thecord associated therewith into connection with the j contacts of acalling-line, so that another subscriber may use the said switch ininitiating another call. I have indicated one such switch 29 upon theleft of the drawing and another upon the right of the drawing for that:the said governor motor is at once in I acondition to beused by anothercalling subscriber,this arrangement being preferred V to thatillustrated m Figs. 1 and 2 in which the governor motor is thrown out ofserv-,

ice until the cord circuit motor selected by it has finished itsoperation in connecting .the answering end of the selected cord'circuitwith the line terminal contacts of a calling subscriber. In thearrangementfil- 'l'ustrated in Figs. and l the answering terminalcontacts of the cord circuit have initial positions to which they arerestored when their cord circuits are disconnected and placed out, ofservice, this arrangement differing from that illustrated in Figs. 1 and2, where the traveling answering ends of the cord circuits remain in thepositions where they were last used. By this arrangement it is apparentthat several cord circuit motors corresponding to a group of telephonelines may be successively started before the controlling ground at theswitch 39 is removed. It will be apparent that by thisapparatus thegovernor motor common to a plurality of lines may be operated in veryquicksuccession, as it is released after starting a cord circuit motorwithout having to be maintained in the position to which it has beenactuated by a calling subscriber until the cord circuit motor haseffected connection between a calling subscriber and an idle cordcircuit. Several cord circuit motorsmay thus be operating at the sametime, the first selected idle cord circuits having connection eil'ectedwith calling lines. That is, the idle cord circuits are connected'u'ithcalling telephone lines in the order in which they have beenselected by the sub scribers governor motor,those started by thegovernor motor in excess of the number calling, which are the last to bestarted, returning to their normal positions. By this arrangement theanswering ends of the cord circuits in sweeping over the line terminalcontacts of a number of calling subscribers stop at the nearest callingline terminal Referring now more particularly to Fig.

3, each subscribers station, AB, is provlded wlth the customary commonbattery ing jack and normally with said switch arms.

arrangements may be employed at the substation. As in the case of thesystems shown in Figs. 1 and 2, the'system indicated need not be limitedto common battery practice. Each subscribers line indicated is ametallio line and extends in two branches to the exchange, where'itterminates in contacts 1,-1"o-f a cut-off relay 22. These contacts arenormally engaged by the armatures of said cut-off relay and arepreferably pivoted contacts and are swung upon their pivots by saidarmatures when unattracted, to a. discontinue the telephone line at thecontacts 1 -1 The upper armature 1 of the relay constitutes a terminalthereof and is The lowerarmature 1' constigrounded.

' The Wins a terminal of the magnet 38.

system illustrated being a. multiple switchboard system, the contacts 1constitute terminals of the office end of the line, which "end issupplied with the line jacks 3 and there are also provided upon othersections of the board thanwhere jack 3 is located, other jacks 1 inconnection with the said contacts 1 1 That which in a multipleswitchboardwould correspond to an answerin any other switch-board wouldcorrespond to a line jack, is fouu d in the multiplev terminals 5-15 andmultiple terminals 66 which are connected with I the telephone lineterminal contacts, as will be understood. The contact buttons orterminals 56 are arranged in circular rows over which sweep theanswering terminals 78 and 7r-8, which answering terminals are connectedwith the answering end of the cord circuit associated therewith, butwhich connection is preferably broken-at the armature switches 91O inthecourseof the selection of a cord circuit, so that the apparatusillustratedmay be effective for the purpose of the invention, the saidarmature switches 910 being included in the tip and sleeve strands ofthe cord circuit, respectivelv, and being serially included in circuitwith the switch arms 7-8 and the contacts 1 1 when said contacts are inconnection There are also provided the additional rows of contactbuttons 12-12 whose general purpose is similar to the purpose of thecorrespondingly designated contacts of Fig. 1, but whose circuitrelations are somewhat modified in view of the altered character ofthe'system of 3. The contactor switch arins-13 3 sweep over contactbuttons 12'12, these the system shown in Fig. stood, for example, thatthirty cord circuits have been assigned to a group of 500 lines,

contact arms being provided' for the same general purpose for which thecorrespondinglydesignate'd contact arms of Flgi 1 are provided, thestructural features of these 7 arms being modified to suit the system'ofFig. 3. These arms, are pivoted at the centers of their circular rows ofcontacts and are flared orenlarged at their free ends, so that they willmake contact with adjacent buttons at the same time, ton will not befreed from connection with a corresi'ionding arm until aftei' thesucceed' ing button has been engaged therebyfiT i that the contactbuttons 5 number 5O0, one

connected with each line, that the number of contact buttons 6 equals500, one connected with each line, and that the numberof contact buttons12 equals 500, one for each line. A The contact brushes T7, 8 a'nd13constitute set and there are as many sets of contact brushes as thei'eare cord circuits assigned to a'group of telephone lines: Said contactarms of each set are desirablyoperated by a common prime mover 15;that'is, there isone prime mover provided forfeaeh of said'sets, whichprimemover may include the shaft 14 upon which said brushes or arms 7, 8and 12 are mounted-gthe spring motor 16, the wheel 17 upon shaft 14;,the said wheel carrying teeth 18-19, arranged in peripheral rows, acrosswhich teeth the polarized armature 2O of the motor is adapted tooscillate by the agency of the field windings 21 and 'thesourceofalternating current 22 when-said source of current is includedin 'a closed circuit ,with said that one but- 3 it maybefunderitsoperation'to the prime mover illustrated upon the left hand of. Fig. 1.I

-VVhen a subscriber initiates a; call, the-faiiswei'ing end of anidlecord circuit, in this Z case the first, is automatically connected witha set of terminal contacts, this automatic connection being occasionedby the operation of thesaid cord cireiiits motor.

in order that the subscribers governor niotor may immediately be usedafter causing a cord circuit motor to start, so that another cordcircuit motor may be soon started'by another calling subscriber withoutwaiting for the first cord circuit motor to complete its operation inselecting an idle cord cir--- curt, the arrangement illustrated ispreferably employed. The governormotor shown upon the left and thatshown upon the right each includes a switch 29 operated fby' thearn'iature of an electro-ma gnet 80, as will-be. hereinafter moreparticularly set V forth,

wi'hich switch QQ'XiClGS over a series of' con-V 2 act buttons 31constituting terminalsyof con- (lHCiiOlS extending to the variouscordcir cuits-of a group, there being'as many co'ntacts 31 as there arecords of a particular lot ass gned to a group of lines, there being anthe example :chosen "thirty such con-tact --buttons A completeconductor32 is shown I the subscribers stations A-B. I

that is, whenits cordcircuit is idle, this extending from 3 one of thecontact buttons 31-to thescord' circult that is shown uniting Normally,

i conductor 32 is connectedwith the grounded battery 23 by wayofth'eswitch :arm 13 whose normal position is upon the contact button-that.engages the switch arm 13 to :eifectconnection of saidconnector withsaid battery. In all of the drawings, for the sake of. clearness, thecontact brushes or flarms are shown as travelling beneath the contactbuttons associated with the same. .:'lhe switch arm 29 is operated bythe mag netgflincluded in-a: circuit that may be traced vfrom thegrounded battery 23, over JthecOnductOr 42-, the .winding adapted forintermittent inclusion in said conductor,

the armatureswitch 44 of relay the ar- "mature switch 39, tothe ground:placed upon j said-armature switch upon'the initiation of arcallhyEacalling subscriber, this armature switch being attracted to effectconnection with saidground because'a circuit is est-ab- I lishedby'sa'id subscriber thi'ough the-magnet 38 operating switch 39 w ien heremoves his't'elephoiie for the purpose of making a "call, which circuitmay be. traced from the f agrounded batter- 23, through the winding -=ofn'iagnet 3-8, the armature 1 over the subscriberstelephoneline 'to thecontact 1 to the grounded armature switch 1 The ,subscribers governor'inotor including the swl toh '29, the operating magnet 30 andassoc'iated :parts,.is similar to the subscribers. governor anotordescribed particularly in connection with Fig. l and are'petitionot'this description will :not, therefore, be req'uired. calling subscriberin initiating a. call, eflects. the travel. of :the switch arm 29 over:the contact buttons 31 until a contact buttonthatis connected withaconductor 32 that isvassociatied with anidle cord circuit sisencountered, whereupon the motor correspond-ingto saidcord circuit .lSset into operation, as will be hereinafter set fort-hr As soon as thecord circuitmotor is set into -operation, that 15,1119011 engagement ofa contact' ''i-l. corresponding to an idle cord ;circuit-(in the case'ofthissystem the'first idle" cord circuit becoming associated withwtjhGfSlVltCll arm 29) the sWltCll arm OI'SWltGh yr29flis immediatelyreciprocated to its initial posit on because the said switch arm is pernnanently grounded through the winding era magnet i5, circuit throughsaid magnet being therefore completed when a conductor -32, grounded, ashas been specified, .at the battery .23, is connected with the element29," the ,magnet 45 serving to attract the armature 44' to 'engage thehook 48 with the detent 46. In orderthatthe spring 49 may becomeeffective in withdrawing the detent operated by the corresponding cordcircuit. motor from the contact of the conductor 32 engaged by saidswitch arm, thereby disconnecting the battery 23 from said conductor 32to open the circuit including the magnet 45, i vhei'eafter the spring4C9'may lift the detent 16 by pulling the catch-1&8

upwardly whereupon the switch 29may be restored by the spring 47.-

Thus, directly after a cord circuit motor has been started to operate bya, governor motor operated by a calling subscriber, the

said governor motor is released, permitting it to act without delay instarting another cord circuit motor in case another subscr ber of thegroup to which the governor motor has been assigned initiates a call; Asupplemental contact 50 is provided so thatthe switch arm 29 may berestored in case all the conductors 32 are associated with busy .cordsor the switch arm 29 has otherwise traveled its full course withouthaving started a cord'circuit motor. The contact but-ton50 is connectedby way of the switch 51 with the grounded battery 23, so that, when theswitch 29 engages said button 50,

circuit through the magnet 45 will be completed to draw up the armatureie and effect engagement of the catch 48 with the detent 46, immediatelywhereafter circuit through the magnet 45 is opened at 51 so that saidmagnet 45 is de-energized and the spring 7 49 is free to liftthe dctent46 by the elevation of the catch 48, whereupon the spring &7reciprocately movesthe switch 29. The

switch arm 13 operated by the selected motor, together with thecompanion switch arms 78, sweep about thelr associated circular rows ofcontacts until the contacts corresponding to the calling line arethereby engaged. Prior'to the connection of the; talking terminalcontacts 78 at the answering end 0t a cord circuit withv acalli-ngsubscribefls line, the armature switches 9-10 are attracted bythe magnet 11" through which circuit is at once established, whichcircuit may be traced from the grounded battery 23, through the Windingof said magnet 11 to the then unattracted armature switch 90 of magnet91, to the contact button in engagement with the selected conductor 32,to the ground at the magnet 45. In the system illustrated in 3 each ofthe contacts 12 is normally grounded at the armature switch 92 operatedby the magnet 38, these grounds being present when the correspondingtelephone lines are idle, but being removed when the magnet 38 isenergized, whichoccurs when a subscriber first initiates a call, theground at 92 being restored as soon as the cut-off relay 2 is energized.There is thus only a brief interval in which the contacts 12 (also 12,etc.) are free of ground. The flared end of thearm13 is consequentlygrounded at thepoints 92, maintaining the magnet 11 energizedauntil thesaid flared end encounters a button12 from which the ground at 92 hasbeen removedby the operation of the magnet 38', whereupon the magnet 11is de-energized to release the armature switches 910, which thereuponcomplete the connection of the selected cord circuit with a callingline. The magnet 91 serves to attract the armature switch 90Vfor thepurpose of preventing the magnet 11 from becoming energized when theground at 92 has been restored. The magnet 91 is not energized, however,until the magnet 93 has become energized, which energization of magnet91 is effected by the closure of the circuit through said magnet 93 thatmay be traced from the grounded battery 23, through the winding of saidmagnet 93, the

. sleeve strand of the cord. circuit, the'armature switch 10, the arm 8,the winding of the cut-oif relay 2 to the ground of said outoff relay.Upon such energization, the armature switch 94 is operated to closecircuit through the magnet 91 to open the circuit containing the magnet11. When the magnet 11 is energized, its armature switch 35 is groundedto "set the selected cord circuit motor in operation. Such energization,as has been stated, is effected immediately upon the engagement of theswitch 29 with a button 31 that is in connection with a switch, such as13, in circuit with an armature switch 90 that is nnattracted becauseoffthe association ofrits, operating magnet 91 with an idle cordcircuit, the ground having been removed at 9% from said magnet 91.

In this way the selected cord circuit motor is started to operate at'once when the subscribers governor motor has performed its functionsaid governor motor thereupon being released as has been specified.l/Vhen.

the magnet 11 has its circuit opened, the prime mover or cord circuitmotor 15 1s thrown out of servlce, as the circuit of the windings 21 isthereupon opened at 35. This: I D 7 again set into operation to securethe restoraopening off the circuit occurs, as has been stated, upon theattraction of the armature switch 90 which is occasioned upon theestablishment of ground at 94, which latter result is not occasioneduntil the calling subscribers line is connected with a cord circuit, Ineffecting the restoration of the traveling answering ends: of the cordcircuits, the switches 7, '8 and 13 continue in their previous directionof rotation, but the polarized armature 20 for this purpose must againbe set inmotion, to which end the magnet 11 must again be energized toground the switch 35.

This result is accompllshed 'by means of the magnet 95 and itsassociated parts Cirin either case the calling subscriber has re-.

stored his telephone), so that the restoration of the answering end ofthe cord circuit may be effected after a subscriber has called andbefore the connection of the selected cord circuit is completed as wellas upon the withdrawal of the connecting plug in the event of itsconnection with the called subscribers line. In either case'the circuitthrough said magnet 95 may be traced from the-ground at 92 (which hasbeen previously restored), to the switch arm 13, the armature switch 90,the winding of the magnet 95, the armature switch 96'of the magnet 97"(which magnet- 97 has been de-energizedbethe energization of the magnet93. The

magnet 95 when energized efiects the closure of circuit through themagnet 11, but inas-.

much as the magnet95 is at once de-energized upon the separation of theswitch 10 from the contact it engages, the circuit closed by the magnet95 must be maintained, to

which end I employ a catch 102 which is en'- gaged by the armature ofthe magnet 95 when attracted. The catch 102 is preferably grounded andthe armature of magnet 95 preferably forms a part of a circuit thatincludes the grounded catch 102, the winding.

of the magnet 11' and the grounded battery 23. The magnet 95 is thusenergized me chanically to connect a ground with the winding of magnet11, to complete its circuit, .whereafter said magnet 95 is de-ene'rQgized, which, however, does not cause the re- J moval of the groundat102. In this way the cord circuit motor or. prime mover is ation ofthe switch parts 7, 8 and "13 to their 7 the polarized armature 20 ,sothat. the switch parts7, 8 and 13 remain in their'initial or normalpositions. In the system illustrated i iii-Fig. 3 the operation ofthecalling lamp 64, the supervisory signals 104eand 105 and the relaysgoverning the same,will be readily understood by an inspection of thediar grain, and I do not, therefore, deem a specific description thereofto be essential: The balanceof the cord circuit apparatus is also well iunderstood by those skilled in the art.

The apparatus shown upon the lower right hand corner of Fig. 3 issimilar inelec trical function to and in some respects is different in.mechanical construction from the apparatus illustrated upon the left01' the figure; The arms 7 8 and 13 correspond 1 Sin function to thearms 7, 8 and 13, but the former arms are designed for rectilinealitravel, to which end certain modification is required in the primemover or cord circuit motor that efiects the travel of said arms, forthey must be adapted for reciprocation insteadoi travel in'acontinuousdirection to effect their purpose. Thegcontact buttons associatedwith'the alr ns'7 8 and .13 are similar in function to thecontactsprovided I in association with the armsT, Sand 13,-

specti'vely, There is, however, an additional butground contact 106 foreach cord-circuit equipped with the arms 7 8 and 13, so

- that in case the said arms should travel their fiillestextent withouteffecting the connectionof a'cord' circuit with a calling line, said arm8 will be grounded to effect the restoration of said contact arms 7 8and 13 as W111 be. specified. The subscribers governor is similar to.W'hen'a conductor 32 has been engaged by a switch arm 13circuit'through the magnet fron the grounded battery 23, through the 107is: closed, which circuit may be traced winding of magnet 107, thearmature switch 108,.the switch arms 13 the conductor 32,

the switch arm 29, to the ground at magnet 45", wi'th results'that willbe understood in viewof the description of the left hand'sub Thearmature. switch 109 is thereby operated to close circuit through thewinding 110 of the motor scri'bers governor motor.

operating the switch arms 7 -'8 and 13 in 1 a manner that is obviouswhen the way in which the switch arm 35 is operated is un- :derstoodfrom the description previously given, and I will not, therefore,describe the motor operating mechanism except to describe certaincircuit changes that occur to change its operative condition. When acord circuit has been connected with a call ing line, circuit throughthe winding 110 is i opened at 109 similarly toithe opening of the '1circuit through the windings at hence, a detailed descriptionoftheoperation of the magnet-107 will not be given. The

conductor 111 that includes the magnet 112 has the same circuitrelations, connections and changes in connections that the conductor 113leading to the switch 94 has; therefore, when the calling subscriber has"been pull upon said catch and eiiect the withdrawalroi' the detent117," so that the arms 7 -8 and 13 may be restored by the spring 122.Circuit through the magnet 11 1 may be traced iiom the ground thrownupon the armature 119 upon the energization of mag net 112 through thewinding of said magnet 11 1, over a conductor 120 in association withthe cord circuit selected, corresponding to conductor 121, to thearmature switch corresponding to the armature switch 96 (nowunattracted, as the magnet 11a is only. to be energized when theanswering 'end of a cord circuit is to be disconnected from thetelephone line united therewith), the now re leased armature SWltCllcorresponding to 98,

to the still attracted armature switch corresponding to'100, thence tothe grounded battery 23. lVhile the magnet 11 1 is energized only whenthe switches 7 8 and 13 are to be restored, the magnet 112 is energizedimmediately upon the connection of a calling line with a cord circuit,whereby the circuit including the magnet 107 is opened at 108 r I tomaintain magnet 107 ole-energized until disconnection. The engagement ofthe parts 116 and 117 (occurring upon disc0nnection as above described),part 117 being grounded, effects the closure of circuit,

through magnetlOi, which circuit may be traced from the grounded battery23, to the magnet 107, the parts 116 and 11-7, to the ground upon part117. The springv 122 restores the cord circuit motor switch arms whenthe dog 117 is withdrawn. Although such circuit is established, it willnow have no control of the winding. 110, circuit through which windingisopened at 115,

but the switches 9'-10 will be moved to disconnect the connecting end ofthe CGlClClP' cuit from thecalling line. The attraction of the switch 10throws. off the ground by which the magnet corresponding to magnet 93has its circuit completed, which ground is at the cut-off relay, so thatthe armature switches of said magnet are released. In this way thecircuit containing the magnet 114: is open at a point corresponding tothe point 100, permitting the spring 118 to withdraw the detent 117. Theinsulating post 116 has separable engagement with the contact 116 forthe mechanical purpose of effecting separation between the elements 116and 117 when the restoration has been completed, ihis'structui alcharacteristic being similar to the similarly illustrated parts ofthesubscribers controller motors; In "case the switch arms 7 8 21110113?should travel to their extreme positions, as would occur should a cordswitch fail to find any calling subscriber after having been started bythe operation of switch 29,"switch-arm 8 will engage the groundedcontact 106 and the circuit through switch-arm 18 will be opened. Theopening of said latter circuit will1cause the de-enerization of magnet10'? and the stopping ofthe motor magnet 110 just as though a callingline had be found. The closing of circuit through the ground 106 Willcause the energization of the magnet corresponding to magnet 93 just asthough a calling line has been selected, thus causing the energizationof magnet 112 and the consequent operation of magnet 11% due to the thenexisting closed contacts in conductor 120 corresponding to contacts 96,98 and 100 in conductor121. The restora'icn of the switch arms to theirnormal positions is thusse'cured by the engagement of hook 116 withdetent 117 and the consequent operation of magnetlO'? andde-energization of magnets 11-2 and 114 just as thoughadisconnectionwere being completed after con- 'nection with a subscribers line.

InFig; 4 is illustrated a system that partakes of the characteristics ofthe systems shown in Figs. 2 and 3 and parts or" the system and circuitsof Fig. 4t corresponding in function to parts and circuits of Figs. 2and 3are given similar characters of reference and I do not deem afurther description of the system shown in Fig. 4 to be essential inview of the extended descriptions hitherto given of the other systems,except that it might be'stated that the magnet 1 91 corrc= sponding infunction to the similarly desig nated magnet of Fig. 3, is connecteddirectly with the conductor 78 which includes the magnet 81 in itscurrent, instead of being included in a local circuit controlled by theoperation of relay 9?), as is done in Fig. 3. In both cases the saidmagnet- 91 is caused to operate as soon as'the circuit through thecutoff relay'Q (Fig. 4-.) 0122 (Fig.3) is completed. The winding ofmagnet 1 12 has a circuit arrangement similar to magnet 91.-

In Fig. 5 I have illustrated the general arrangement of the circuits andapparatus that I prefer, but in this figure I have not hadsulficientroom to illustrate to the fullest extent all of the apparatusinvolved, but the general features of the system'will be understood byreference to the following description. 1

I have illustrated three groups of telephone lines, I, II and III. Eachgroup may be understood as containing 500 lines to carry out theillustration set forth in the introduction to this specification. Therectangular figures aaa each indicates a subscribers governor I motor.or selecting switching mechanism that may have su table control,preferably by means-of the circuits and apparatus illustrated (either inFigsl. and 2 or Figs. 3 and 4),o:t' the cord circuit motors 15. Theoperative connections be'-. tween the elements a and l5areliiidicated bydotted lines, The answering ends of the cord circuits includingthe-traveling switch arms 77, 88" and 1313, etc.-,. in the} case ofFigs. 1 and3, and also the switch arms 77+? 7 etc., in the case of Figs.2 and 4:, are indicated at b. The contacts over 7 which the travelingswitch arms last men tioned -move are indicated by the circles 0., eachcirclelndicat ng a complete group ot line contacts in operativeassociation.[withv the answering end of the cord circuit, each lines inthe system. shown'as an example- It will be apparent by thedescriptionpreviously given and by the illustration in Fig.

5, that the first idle cord circuit is connected with a calling line,the busy cords or those cords made to correspondto busy'cords: by theelements 52 being skipped. Reading 5 it'rom left to right, the answeringend Z) of the first cord circuit (referring now to group I of the lines)is connected with thefirst plug at the first position ot' the firstsection of the board. The answeringend of the second cord circuit isconnected with the first plug at the second position of the firstsection of the board. The third answering end is connected with thefirst 'plugat'thc third position of the first section of the board. Thefourth answering end is (connected with the first plug at the firstposi' tion of the second section of the-board.

.The fifth answering endis connected with thirty answering ends of thecordcircuits' at ten sections of the board);

Referring to group II, the first answering end is connected with thesecond plug at the first position of the first sectionof the board. Thesecond answering end is con nected with the. secondfplug at the secondposition of the first section of'theboard;

The third answering end is connected with the second plug at thethirdlposition of lost

